Traditional methods for building a color measurement device typically involve high-precision optics, complex mirrors/prisms, sophisticated illumination systems, and/or specialized processing capabilities (e.g., low-noise analog-to-digital converters). The advent of the digital imaging chip—although intended to capture moving or still images—created an intriguing alternative “engine” for making a color measurement based on it's simplicity and low cost.
However, digital imaging chips, when used as intended to capture images, are typically ineffective at making precise color measurements. This is due in part to the large amount of data generated by each image. This massive amount of data from the “raw” image must be compressed to increase their transmission rate and color information is typically lost in this process. For a color measurement at a specific point, only of fraction of the total image data is relevant anyway—the rest is superfluous. Finally, most imaging chips have built-in features that make automatic adjustments (e.g., of shutter width and sensitivity). These allow the chip to produce good images under a wide variety of conditions and in changing conditions. However these features become a barrier to an accurate color measurement, as they can make the response of the chip to a color stimulus unpredictable. All of these factors combine with the fundamental instabilities and noise inherent in a typical analog-digital electronic system to limit an imaging chip's ability to make precise, accurate, and repeatable color measurement.
The purpose of this patent is to describe a method that overcomes these obstacles, and can make a digital imaging chip a viable means for making a color measurement.